The present invention relates to a novel pitch material having specific characteristics and useful for the manufacture of a carbonaceous body or, in particular, carbon fiber as well as a method for the preparation of such a pitch material.
In the prior art, carbon fibers are mostly manufactured by the calcination of fibrous bodies obtained by spinning polyacrylonitrile. This process is, however, disadvantageous due to the expensiveness of the starting polymer and the low carbonization yield in the calcination. Therefore, many attempts and proposals have been made recently for the manufacture of carbon fibers from pitch materials of petroleum origin or coal tar origin as the starting material.
Among these prior art methods for the manufacture of pitch-based carbon fibers, for example, a method is proposed in Japanese Patent Kokai Koho Nos. 58-18421, 58-115120, 58-142976, 58-154792 and others according to which spinning of the starting pitch is performed at a temperature higher than the softening point of the pitch by 60.degree. to 130.degree. C. A problem encountered in the spinning process at such a relatively high spinning temperature is the thermal decomposition of the pitch and foaming of the molten pitch so that the process requires a starting pitch material having a softening point as low as possible. A pitch material having a low softening point should have characteristics that the content of the pyridine- or quinoline-soluble matter therein is low and the molecular weight thereof should be relatively small with a broad molecular weight distribution. The carbon fiber-manufacturing process using such a pitch material is, however, disadvantageous because a lengthy time is taken for the infusibilization treatment following spinning of the pitch material.